Classifications

• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K9/00—Screening of apparatus or components against electric or magnetic fields
• • H—ELECTRICITY
  • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
  • H05K—PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
  • H05K9/00—Screening of apparatus or components against electric or magnetic fields
  • H05K9/0073—Shielding materials
  • H05K9/0081—Electromagnetic shielding materials, e.g. EMI, RFI shielding
  • H05K9/0088—Electromagnetic shielding materials, e.g. EMI, RFI shielding comprising a plurality of shielding layers; combining different shielding material structure
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/34—Layered products comprising a layer of synthetic resin comprising polyamides

Definitions

• the present invention relates to electromagnetic shielding articles suitable for use in electromagnetic interference (EMI) shielding applications.
• the present invention relates to multilayer electromagnetic shielding articles that significantly increase shielding effectiveness.
• the present invention provides a shielding article including a first conductive layer and a second conductive layer spaced apart from the first conductive layer by a non-conductive polymeric layer defining a separation distance.
• the first conductive layer and the second conductive layer cooperatively provide a first shielding effectiveness.
• the first conductive layer, the second conductive layer, and the separation distance cooperatively provide a second shielding effectiveness that is greater than the first shielding effectiveness.
• the present invention provides a shielding article including a plurality of conductive layers, each conductive layer spaced apart from an adjacent conductive layer by a non-conductive polymeric layer defining a separation distance.
• the conductive layers cooperatively provide a first shielding effectiveness.
• the conductive layers and separation distances cooperatively provide a second shielding effectiveness that is greater than the first shielding effectiveness.
• Fig. 1 is a schematic cross-sectional view of an exemplary embodiment of a shielding article according to an aspect of the present invention.
• Fig. 2 is a schematic cross-sectional view of another exemplary embodiment of a shielding article according to an aspect of the present invention.
• Fig. 3 is a schematic cross-sectional view of another exemplary embodiment of a shielding article according to an aspect of the present invention.
• Fig. 4 is a schematic cross-sectional view of another exemplary embodiment of a shielding article according to an aspect of the present invention.
• Fig. 5 is a graph illustrating the improved shielding effectiveness achieved by shielding articles according to aspects of the present invention.
• Fig. 6 is another graph illustrating the improved shielding effectiveness achieved by shielding articles according to aspects of the present invention.
• the present invention includes a multi-layer shielding article that is useful for shielding of electronic communications devices by interfering with or cutting off the electrical or magnetic signal emitted from electromagnetic equipment, electronics equipment, receiving devices, or other external devices.
• Fig. 1 illustrates an exemplary embodiment of a shielding article according to an aspect of the present invention.
• Shielding article 100 includes a first conductive layer 102a and a second conductive layer 102b (collectively referred to herein as "conductive layers 102"). Second conductive layer 102b is spaced apart from first conductive layer 102a by a non-conductive polymeric layer 104.
• Non-conductive is defined herein as substantially not electrically conductive.
• Polymeric layer 104 defines a separation distance A, which in this embodiment substantially corresponds with the thickness of polymeric layer 104.
• First conductive layer 102 a and second conductive layer 102b cooperatively provide a first shielding effectiveness.
• the first shielding effectiveness is based on a double-thickness single conductive layer which is effectively equal to two adjacent single-thickness conductive layers 102a and 102b.
• first conductive layer 102a, second conductive layer 102b, and separation distance A cooperatively provide a second shielding effectiveness that is greater than the first shielding effectiveness.
• Conductive layers 102 may be formed by metalizing polymeric layer 104, such as, e.g., by chemical deposition (such as, e.g., electroplating), physical deposition (such as, e.g., sputtering), or any other suitable method. Alternatively, conductive layers 102 may be laminated onto polymeric layer 104. In one embodiment, conductive layers 102 each have a thickness in the range of 100 to 30000 Angstroms (10 to 3000 nm). In the embodiment of Fig. 1, conductive layers 102a and 102b have substantially the same thickness. In other embodiments, conductive layers 102a and 102b may have a different thickness.
• Conductive layers 102 may include any suitable conductive material, including but not limited to copper, silver, aluminum, gold, and alloys thereof.
• First conductive layer 102a may include a different material or combination of materials than second conductive layer 102b.
• first conductive layer 102a may include a layer of copper and second conductive layer 102b may include a layer of silver.
• Polymeric layer 104 may include any suitable polymeric material, including but not limited to polyester, polyimide, polyamide-imide, polytetrafluoroethylene, polypropylene, polyethylene, polyphenylene sulfide, polyethylene naphthalate, polycarbonate, silicone rubber, ethylene propylene diene rubber, polyurethane, acrylate, silicone, natural rubber, epoxies, and synthetic rubber adhesive.
• Polymeric layer 104 may include one or more additives and/or fillers to provide properties suitable for the intended application. Adhesive materials, additives, and fillers that may be included in polymeric layer 104 are described in more detail below.
• Polymeric layer 104 may include non- wovens, fabrics, foams, or a substantially hollow polymeric or adhesive layer. In one embodiment, polymeric layer 104 has a thickness in the range of 5 ⁇ m to 500 ⁇ m. In the embodiment shown in Fig. 1, first and second conductive layers 102a and
• Nickel layers 108 and copper layers 106 are deposited using any suitable method known in the art.
• Polymeric layer 104 provides sufficient flexibility for the final use of shielding article 100, while it also has sufficient rigidity, thermal stability, and chemical stability, e.g., for use in the metal deposition process.
• Nickel layers 108 provide better adhesion of copper layers 106 to polymeric layer 104 than copper layers 106 alone.
• Copper layers 106 provide sufficient electrical conductivity to allow the construction to act as a shielding article for use in mobile phones, televisions, gaming electronics, cameras, RFID security devices, medical devices, and electronic devices in automotive and aerospace applications, for example.
• an additional layer of nickel may be deposited onto the outer surface of copper layers 106 to provide corrosion protection to copper layers 106.
• nickel layers 108 each have a thickness in the range of 25 to 125 Angstroms (2.5 to 12.5 nm) and copper layers 106 each have a thickness in the range of 50 to 2000 Angstroms (5 to 200 nm).
• nickel layers 108 each have a thickness in the range of 50 to 100 Angstroms (5 to 10 nm) and copper layers 106 each have a thickness in the range of 800 to 2000 Angstroms (80 to 200 nm).
• the preferred ranges of material thickness allow a desired balance of material flexibility and reliability, while providing adequate amounts of material for electrical conductivity and corrosion protection.
• copper layers 106a and 106b have substantially the same thickness, in other embodiments, copper layers 106a and 106b may have a different thickness.
• nickel layers 108a and 108b have substantially the same thickness, in other embodiments, nickel layers 108a and 108b may have a different thickness.
• Nickel layers 108 are defined herein as layers including at least one of nickel (Ni), nickel alloys, and austenitic nickel-based superalloys, such as, e.g., the austenitic nickel-based superalloy available under the trade designation INCONEL from Special Metals Corporation, New Hartford, New York, U.S.A.
• Copper layers 106 are defined herein as layers including at least one of copper (Cu) and copper alloys.
• Fig. 2 illustrates another exemplary embodiment of a shielding article according to an aspect of the present invention.
• Shielding article 200 includes shielding article 100 as described above and an adhesive layer 210 disposed on first conductive layer 102a.
• an adhesive layer 210 may be disposed on second conductive layer 102b or on both first and second conductive layers 102a, 102b.
• adhesive layer 210 is used to bond shielding article 200 to a protective layer, or a device or component that needs to be electromagnetically shielded, for example.
• Adhesive layer 210 may include a pressure sensitive adhesive (PSA), a hot melt adhesive, a thermoset adhesive, a curable adhesive, or any other suitable adhesive.
• PSA pressure sensitive adhesive
• Adhesive layer 210 may include one or more additives and/or fillers to provide properties suitable for the intended application. Adhesive materials, additives, and fillers that may be included in adhesive layer 210 are described in more detail below. Adhesive layer 210 may include a corrosion inhibitor. In one embodiment, adhesive layer 210 has a thickness in the range of 10 ⁇ m to 150 ⁇ m.
• Fig. 3 illustrates another exemplary embodiment of a shielding article according to an aspect of the present invention.
• Shielding article 300 includes shielding article 200 as described above and a protective layer 312 disposed adjacent adhesive layer 210.
• protective layer 312 is bonded to first conductive layer 102a by adhesive layer 210.
• a protective layer 312 may be disposed adjacent second conductive layer 102b or adjacent both first and second conductive layers 102a, 102b.
• protective layer 312 includes a polyester paper coated with an inorganic coating, such as, e.g., the polyester paper coated with an inorganic coating available under the trade designation TufQUIN from 3M Company, St. Paul, Minnesota, U.S.A.
• protective layer 312 includes an aramid paper, such as, e.g., the aramid paper available under the trade designation NOMEX from E. I. du Pont de Nemours and Company, Wilmington, Delaware, U.S.A.
• aramid paper such as, e.g., the aramid paper available under the trade designation NOMEX from E. I. du Pont de Nemours and Company, Wilmington, Delaware, U.S.A.
• Protective layer 312 is typically capable of offering chemical protection (such as, e.g., protection against corrosion) as well as physical protection (such as, e.g., protection against abrasion).
• Protective layer 312 may have any thickness suitable for the intended application.
• Fig. 4 illustrates another exemplary embodiment of a shielding article according to an aspect of the present invention.
• Shielding article 400 includes a first conductive layer 102a and a second conductive layer 102b as described above. Second conductive layer
• Polymeric layer 404 defines a separation distance B, which in this embodiment substantially corresponds with the thickness of polymeric layer 404.
• First conductive layer 102a and second conductive layer 102b cooperatively provide a first shielding effectiveness.
• first conductive layer 102a, second conductive layer 102b, and separation distance B cooperatively provide a second shielding effectiveness that is greater than the first shielding effectiveness.
• Polymeric layer 404 includes a first non- conductive polymeric sublayer 414a, a second non-conductive polymeric sublayer 414b, and a bonding adhesive layer 416 disposed between first polymeric sublayer 414a and second polymeric sublayer 414b.
• first and second polymeric sublayers 414a and 414b are identical to polymeric layer 104 as described above.
• a useful advantage of this construction of polymeric layer 404 is in the method of making shielding article 400.
• shielding article 400 is made as follows: First, conductive layer 102a is deposited onto first polymeric sublayer 414a, and second conductive layer 102b is deposited onto second polymeric sublayer 414b, resulting in two separate constructions. Then, bonding adhesive layer 416 is laminated to first polymeric sublayer 414a, and second polymeric sublayer 414b is laminated to bonding adhesive layer 416, combining the two separate constructions into shielding article 400.
• Bonding adhesive layer 416 may include a pressure sensitive adhesive (PSA), a hot melt adhesive, a thermoset adhesive, a curable adhesive, or any other suitable adhesive. Bonding adhesive layer 416 may include one or more additives and/or fillers to provide properties suitable for the intended application. Adhesive materials, additives, and fillers that may be included in bonding adhesive layer 416 are described in more detail below. Adhesive layers of a shielding article according to an aspect of the present invention, such as, e.g., adhesive layers 210 and 416, may include any of the various types of materials used for bonding, adhering, or otherwise affixing one material or surface to another.
• PSA pressure sensitive adhesive
• Bonding adhesive layer 416 may include one or more additives and/or fillers to provide properties suitable for the intended application. Adhesive materials, additives, and fillers that may be included in bonding adhesive layer 416 are described in more detail below. Adhesive layers of a shielding article according to an aspect of the present invention, such as
• Classes of adhesives include, for instance, pressure sensitive adhesives, hot melt adhesives, thermoset adhesives, and curable adhesives.
• the pressure sensitive adhesives include those based on silicone polymers, acrylate polymers, natural rubber polymers, and synthetic rubber polymers. They may be tackified, crosslinked, and/or filled with various materials to provide desired properties. Hot melt adhesives become tacky and adhere well to substrates when they are heated above a specified temperature and/or pressure; when the adhesive cools down, its cohesive strength increases while retaining a good bond to the substrate.
• hot melt adhesives examples include, but are not limited to, polyamides, polyurethanes, copolymers of ethylene and vinyl acetate, and olef ⁇ nic polymers modified with more polar species such as maleic anhydride.
• Thermoset adhesives are adhesives that can create an intimate contact with a substrate either at room temperature or with the application of heat and/or pressure. With heating, a chemical reaction occurs in the thermoset to provide long term cohesive strength at ambient, subambient, and elevated temperatures.
• thermoset adhesives include epoxies, silicones, and polyesters, and polyurethanes.
• Curable adhesives can include thermosets, but are differentiated here in that they can cure at room temperature, either with or without the addition of external chemical species or energy. Examples include two-part epoxies and polyesters, one -part moisture cure silicones and polyurethanes, and adhesives utilizing actinic radiation to cure such as UV, visible light, or electron beam energy.
• Non-conductive polymeric layers and adhesive layers of a shielding article according to an aspect of the present invention may include various types of additives and fillers alone or in combination to provide properties suitable for the intended application.
• Typical additives and fillers include plasticizers, thermal stabilizers, antioxidants, UV stabilizers, pigments, dyes, flame retardants, smoke suppressants, conductive fillers, species to improve chemical resistance, and other property modifiers. Flame retardants represent another class of filler useful for some applications to ensure that the overall product construction minimizes, ameliorates, or eliminates the propagation of fire.
• Types of flame retardants can include halogenated flame retardants such as decabromo dipehnyl oxide, chlorinated paraffin wax, brominated phenols, and brominated bisphenol A. Furthermore, formulations which employ halogenated flame retardants often include antimony oxides such as antimony trioxide which act synergistically to enhance the flame retarding abilities of the halogen compound.
• halogenated flame retardants such as decabromo dipehnyl oxide, chlorinated paraffin wax, brominated phenols, and brominated bisphenol A.
• antimony oxides such as antimony trioxide which act synergistically to enhance the flame retarding abilities of the halogen compound.
• intumescent flame retardants include phosphates such as ammonium polyphosphate and nitrogen compounds such as melamine.
• phosphates such as ammonium polyphosphate
• nitrogen compounds such as melamine.
• flame retardants include molybdenates and borates which also suppress smoke generation. Some examples of these types of flame retardants include ammonium octomolybdenate and zinc borate. Any combination of these and other well known flame retardants may be included.
• fillers include titanium dioxide, fumed silica, carbon fibers, carbon black, glass beads, glass fibers, glass bubbles, mineral fibers, clay particles, organic fibers, zinc oxide, aluminum oxide, boron nitride, aluminum nitride, barium titanate, molybdenum and the like.
• the conductive particles can be any of the types of particles currently used, such as spheres, flakes, rods, cubes, amorphous, or other particle shapes. They may be solid or substantially solid particles such as carbon black, carbon fibers, nickel spheres, nickel coated copper spheres, metal-coated oxides, metal-coated polymer fibers, or other similar conductive particles. These conductive particles can be made from electrically insulating materials that are plated or coated with a conductive material such as silver, aluminum, nickel, or indium tin-oxide.
• the metal-coated insulating material can be substantially hollow particles such as hollow glass spheres, or may comprise solid materials such as glass beads or metal oxides.
• the conductive particles may be on the order of several tens of microns to nanometer sized materials such as carbon nanotubes.
• the conductive adhesive can also be comprised of a conductive polymeric matrix.
• Shielding articles according to aspects of the present invention have numerous advantages for their intended use as compared to conventional shielding articles.
• One particular advantage is an unexpected performance in electromagnetic shielding, which is described in greater detail below. Examples
• Shielding effectiveness measurements on shielding articles according to aspects of the present invention and on conventional shielding articles were conducted.
• the shielding effectiveness measurements were conducted generally following the Standard Test Method for Measuring the Electromagnetic Shielding Effectiveness of Planar Materials ASTM D 4935-99. Measurements were performed on an Agilent Technologies N5230A PNA-L Network Analyzer outfitted with a TEM cell, and the IF Bandwidth and number of scans averaged were adjusted as necessary to accurately measure the shielding level of the various samples. The following test samples were prepared.
• Comparative test sample C501 was a sample of a conventional shielding article including a single conductive layer deposited onto a non-conductive polymeric layer. Specifically, comparative test sample C501 was created as follows: A layer of nickel having a thickness of about 75 Angstroms (7.5 nm) was deposited onto a polymeric layer including polyethylene terephthalate and having a thickness of about 2.0 mil (51 ⁇ m). A layer of copper having a thickness of about 1100 Angstroms (110 nm) was deposited onto the layer of nickel.
• test sample 503 was created as follows: A first layer of nickel having a thickness of about 75 Angstroms (7.5 nm) was deposited onto a first polymeric layer including polyethylene terephthalate and having a thickness of about 2.0 mil (51 ⁇ m). A first layer of copper having a thickness of about 550 Angstroms (55 nm) was deposited onto the first layer of nickel. A second layer of nickel having a thickness of about 75 Angstroms (7.5 nm) was deposited onto a second polymeric layer separate from the first polymeric layer. A second layer of copper having a thickness of about 550
• Test sample 504 was a sample of another shielding article according to an aspect of the present invention. Specifically, test sample 504 was created as follows: A first layer of nickel having a thickness of about 75 Angstroms (7.5 nm) was deposited onto a first polymeric layer including polyethylene terephthalate and having a thickness of about 2.0 mil (51 ⁇ m).
• a first layer of copper having a thickness of about 550 Angstroms (55 nm) was deposited onto the first layer of nickel.
• a second layer of nickel having a thickness of about 75 Angstroms (7.5 nm) was deposited onto a second polymeric layer separate from the first polymeric layer.
• a second layer of copper having a thickness of about 550 Angstroms (55 nm) was deposited onto the second layer of nickel.
• a bonding adhesive layer including an acrylate pressure sensitive adhesive and having a thickness of about 5.0 mil (127 ⁇ m) was laminated to the first polymeric layer. The second polymeric layer was laminated to the bonding adhesive layer.
• Table 1 and Fig. 5 present the shielding data, averaged from 100 to 1000 MHz for samples C501-504.
• the shielding effectiveness of comparative test sample C501 was measured at -55.7 dB over the range of 100 through 1000 MHz.
• the shielding effectiveness was unexpectedly increased to -66.9 dB (-11.2 dB additional shielding). This data illustrates that the presence of a separation distance between conductive layers of a shielding article unexpectedly increases the shielding effectiveness of the shielding article.
• Comparative test sample C601 was a sample of a conventional shielding article including a single conductive layer including an aluminum foil having a thickness of about 0.9 mil (23 ⁇ m).
• Test sample 602 was a sample of a shielding article according to an aspect of the present invention. Specifically, test sample 602 was created as follows: A first conductive layer including an aluminum foil having a thickness of about 0.4 mil (10 ⁇ m) was laminated to a polymeric layer including acrylate bonding adhesive having a thickness of about 1.0 mil (25 ⁇ m). A second conductive layer including an aluminum foil having a thickness of about 0.4 mil (10 ⁇ m) was laminated to the opposing surface of the polymeric layer.
• Test sample 603 was a sample of a shielding article according to an aspect of the present invention. Specifically, test sample 603 was created as follows: A first conductive layer including an aluminum foil having a thickness of about 0.4 mil (10 ⁇ m) was laminated to a polymeric layer including acrylate bonding adhesive having a thickness of about 2.0 mil (51 ⁇ m). A second conductive layer including an aluminum foil having a thickness of about 0.4 mil (10 ⁇ m) was laminated to the opposing surface of the polymeric layer.
• Test sample 604 was a sample of a shielding article according to an aspect of the present invention. Specifically, test sample 604 was created as follows: A first conductive layer including an aluminum foil having a thickness of about 0.4 mil (10 ⁇ m) was laminated to a polymeric layer including acrylate bonding adhesive having a thickness of about 4.0 mil (102 ⁇ m). A second conductive layer including an aluminum foil having a thickness of about 0.4 mil (10 ⁇ m) was laminated to the opposing surface of the polymeric layer.
• Test sample 605 was a sample of a shielding article according to an aspect of the present invention. Specifically, test sample 605 was created as follows: A first conductive layer including an aluminum foil having a thickness of about 0.4 mil (10 ⁇ m) was laminated to a polymeric layer including acrylate bonding adhesive having a thickness of about 6.0 mil (152 ⁇ m). A second conductive layer including an aluminum foil having a thickness of about 0.4 mil (10 ⁇ m) was laminated to the opposing surface of the polymeric layer. Table 2
• Table 2 and Fig. 6 present the shielding data, averaged from 100 to 1000 MHz of samples C601-605.
• the shielding effectiveness of comparative test sample C601 was measured at -112.1 dB over the range of 100 through 1000 MHz.
• the shielding effectiveness was unexpectedly increased to -123.4 dB (-11.3 dB additional shielding).
• This data illustrates that the presence of a separation distance between conductive layers of a shielding article unexpectedly increases the shielding effectiveness of the shielding article.
• Test sample 701 was a sample of a shielding article according to an aspect of the present invention. Specifically, test sample 701 was created as follows: A layer of nickel having a thickness of about 150 Angstroms (15 nm) was deposited onto a polymeric layer including polyethylene terephthalate and having a thickness of about 2.0 mil (51 ⁇ m). A layer of copper having a thickness of about 1800 Angstroms (180 nm) was deposited onto the layer of nickel. A layer of titanium having a thickness of about 150 Angstroms (15 nm) was deposited onto the opposing surface of the polymeric layer. A layer of silver having a thickness of about 1000 Angstroms (100 nm) was deposited onto the layer of titanium.
• test sample 701 The average shielding effectiveness of test sample 701 was measured at -81.6 dB, whereby 4 specimens were averaged.
• This example demonstrates that a shielding article wherein a first conductive layer and a second conductive layer include different conductive materials can be utilized effectively. It also demonstrates that the thickness of the first and second conductive layers may be different.
• a shielding article including a first conductive layer spaced apart from a second conductive layer has a greater shielding effectiveness than a shielding article wherein the first conductive layer and the second conductive layer essentially form a single conductive layer (i.e., single layer construction).
• a shielding article including a plurality conductive layers, each conductive layer spaced apart from an adjacent conductive layer i.e., multi-layer construction
• the shielding effectiveness of the shielding article will further increase.

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• Engineering & Computer Science (AREA)
• Microelectronics & Electronic Packaging (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Laminated Bodies (AREA)
• Shielding Devices Or Components To Electric Or Magnetic Fields (AREA)

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• 2010
  • 2010-05-19 US US12/782,746 patent/US20100300744A1/en not_active Abandoned
  • 2010-05-19 CN CN2010800327297A patent/CN102461362A/zh active Pending
  • 2010-05-19 WO PCT/US2010/035341 patent/WO2010138348A2/en active Application Filing
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  • 2010-05-19 CA CA2762218A patent/CA2762218A1/en not_active Abandoned
  • 2010-05-19 JP JP2012513127A patent/JP2012528485A/ja active Pending
  • 2010-05-19 KR KR1020117030995A patent/KR20120017458A/ko not_active Application Discontinuation
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